Various kinds of motors are available such as a brushed DC motor, an induction motor, and a PM motor, each of the motors having a single phase, three phases, or the like. Among these various motors, the single-phase PM motor does not use a brush that is a mechanical structure. For such a “brushless” structure of the single-phase PM motor, there is no brush wear unlike the brushed DC motor. This feature allows the single-phase PM motor to easily achieve long service life and high reliability.
Moreover, the single-phase PM motor is a highly efficient motor as compared with the induction motor because no secondary current flows to a rotor of the single-phase PM motor.
The single-phase PM motor also has the following advantages as compared with a three-phase PM motor having the number of phases different from that of the single-phase PM motor. The three-phase PM motor requires a three-phase inverter, whereas the single-phase PM motor requires only a single-phase inverter. The use of a commonly used full-bridge inverter as the three-phase inverter requires six switching elements, whereas the use of the full-bridge inverter in the single-phase PM motor requires four switching elements. Thus, an apparatus with the single-phase PM motor can be made smaller than with the three-phase PM motor.
The following Patent Literature 1 and Non Patent Literature 1 are disclosed as examples of prior literature relating to a system of driving the single-phase PM motor.